Posts by Mr Spuratic

Re: Question

Yes, there is no pipe.

1&>- causes FD 1 (stdout) to be closed, but not to save the user from noise, this is setuid hacking 101. With FD 1 closed, the next call to fopen() will reuse the now freed up FD 1, so output intended for the user will instead end up in the opened file (disk device), effectively junking it. See pages 53-57 of Esser's paper linked from the article.

(The "[n]>&word" form is for duplicating FDs, with "-" as special case for closing the FD.)

Re: Technical pedantry

Yes, unqualified "brute force" is not the proper term here, I mean the (probably) expensive computation involved in attacks similar to that you describe. This will be by definition better than exhaustive brute force, if and when the cat is let out of the bag.

Since the collision attack you describe was used in the 2009 hashclash MD5 attack it is no longer as trivial, CAs must use random serial numbers. My understanding is that further increasing signing-time entropy would have provided continued protection, which is why I'm hoping Santa Claus will bring a second-preimage attack this year.

Re: DNS and hyphens

I'm talking about ASCII 0x2D, strictly IA5 "hyphen (minus)", informally "dash", and what's allowed in the "ASCII" subset letter-digit-hyphen, as historically used in DNS labels. A feature of IDN, which presumably justifies its complexity, is that it is backward compatible with this (ignoring the fact that a label is simply an octet sequence and technically need not be 7 bit ASCII).

One (my) interpretation of the above statement from the article is that the hyphen/dashes in the ACE "xn--" prefix or separator are going to cause problems. The encoded value cannot contain either a leading or trailing hyphen/dash (see RFC 3492 section 5), so where's the new problem?

There are other far less plausible (to me) interpretations, possibly involving systems that decode IDNs and reject dashes for some reason.

FWIW, valid IDN encompasses a large subset of Unicode, including all the dashes you might need or want. Further reading: Unicode Consortium IDN FAQ, reports TR36 & TR46, and the IDNA2008 RFCs 5890-5894 (get cracking, it's less than 5 hours until beer o'clock, this will be on the test ;-)

Re: What is systemd

This is under active development: http://uselessd.darknedgy.net/

There are no doubt other efforts too.

Neat hack, misleading headline

SHA-1 wasn't designed to be slow, it was designed to be "cryptographically secure". This is why proper password implementations which use any type of hashing have multiple rounds and salt ("PBKDF" and "password strengthening" are terms associated with these).

Read http://www.akkadia.org/drepper/SHA-crypt.txt for a real password implementation (which uses SHA-2 rather than SHA-1, but the principle is the same).

5000 rounds + 16 characters of salt makes brute-force a *lot* harder. Approx 2^108 times harder, if you don't have the salt, and only ~2^12 if you do (making a 2 hour exercise into a ~12 month exercise). I've read the results, the input file had one hash round.

I see a neat hack (nicely documented too) showing what you can do with EC2, and a misleading headline... "crack sha-1 hashes" != "crack sha-1 hashing"

Wake me up when someone uses EC2 to find useful SHA-1 collisions :)